In the prior art, there exists a certain number of methods intended to detect a chemical substance, particularly when the chemical substance is an acid or a base.
Thus, it has been known for a long time to resort to the technique of pH paper to detect whether a liquid medium contains an acid or a base. This pH paper is soaked with a universal indicator, which is designed to change colour gradually as a function of the pH. This universal indicator conventionally corresponds to a mixture of coloured indicators, each of the coloured indicators of the mixture having one or even two change of colour zones for well determined pH ranges. The coloured indicators are chosen in such a way as to make it possible, thanks to the change of colour that has taken place, to obtain rapidly the pH of a solution, and are also capable of covering pHs ranging from 0 to 14.
Nevertheless, this method of detection stems from a direct wish of the user to detect the presence of a given chemical substance and does not enable the detection of such a substance without the intervention of said user. In other words, the aforementioned method does not enable the unexpected leak of a chemical substance to be spontaneously detected, in an environment where such a leak is prohibited.
To offset this insufficiency, other authors have imagined using the principle of the detection of a chemical substance by coloured indicators by impregnating fabrics with such substances and making, from these fabrics, clothing intended to be worn by users in contact with environments where it is important to detect spontaneously the presence of a chemical substance, for example following a leak of said substance, which could be at the origin of an industrial incident if the problem is not checked.
Thus, the user finding himself, in the context of his activities, in unexpected contact with the undesirable substance, could immediately observe a change of colour of his outfit and thus avert any incident by immediately resolving the problem of the leak of the undesirable substance.
This is the case of clothing conceived from fabrics impregnated with a resin containing a coloured indicator able to change colour in the presence of a given chemical substance, more precisely in the presence of an acid substance.
Nevertheless, this type of embodiment has the following drawbacks:                the fabrics used do not make it possible to detect precisely the nature of the acid substance, which has entered into contact with them;        the fabrics used are difficult to upkeep, because the coloured indicators impregnating the fabric may be eliminated in part during washing.        
There thus exists a real need for fabrics, which can enter into the constitution of safety clothing, capable of detecting the presence of a chemical substance, which fabrics do not have the drawbacks of those of the prior art.